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In the last decades, the studies involving the mechanisms of the CO2 emissions dynamics have been studied in several ecosystems with varied soil classes. The objective of this study was to evaluate the relationship between physical and chemical attributes of soils and the variation of CO2 efflux in Indian Black Earth (IBE) and non-anthropogenic soils in the Amazon. The study areas are located in the southern region of Amazonas, specifically in the municipalities of Humaitá and Apuí. Respectively in the natural field and forest areas, grids with dimensions of 70 m x 70 m and 10 m regular spacing between sample points, in the depth of 0.0–0.20 m, totaling 64 samples were delimited. In the IBE area, a 42 x 88 m grid was established, marking points at a 6 x 8 m spacing, totalizing 88 sampling points in the depth of 0.0–0.2 m. The soil physical analyzes performed were bulk density, soil penetration resistance, macroporosity, microporosity, total porosity and texture, and the soil chemical analyzes were composed by organic carbon, organic matter and carbon stocks. The soil CO2 emission (FCO2) was recorded with a portable automated LI-COR soil flow system (LI-8100). The soil temperature (Tsolo) was monitored concomitantly with the soil CO2 emission evaluations using a temperature sensor that is an integral part of the LI-8100 system. Soil moisture was recorded using a Time Domain Reflectometry (TDR) apparatus - Campbel® Hydrosense ™ Campbell Scientific. The data were submitted to descriptive statistical analyzes and multiple linear regression with the pedotransfer functions model criterion. The study demonstrates the variation of physical and chemical attributes of the soil and its influence on CO2 efflux variation, since the different environments studied presented differentiated scales and attributes for each situation, due to the correlations presented.

O conhecimento dos danos provocados pelos diferentes sistemas de manejo é essencial para melhorar a qualidade física do solo. Assim o objetivo deste trabalho foi avaliar os atributos físicos do solo em áreas sob diferentes sistemas de usos na região de Manicoré, AM. Foram delimitadas três áreas, com os seguintes usos do solo: área cultivada com milho, área cultivada com pastagem e área sob floresta nativa. Foram coletadas 32 amostras de solos nas profundidades de 0,0-0,10 m em cada uma das três áreas estudadas. Os atributos físicos avaliados foram: textura, resistência do solo a penetração, umidade do solo, macroporosidade, microporosidade, porosidade total, densidade do solo e de partícula e estabilidade dos agregados. Foram realizadas análises de variância uni e multivariadas e os resultados dos diferentes sistemas de usos foram comparados pelo teste de Tukey a 5% de probabilidade. Os sistemas de usos alteram os atributos do solo, especialmente a densidade do solo, macro e microporosidade do solo, resistência do solo a penetração e volume total de poros. A maior percentagem de agregados com maiores diâmetros foi encontrada no sistema de uso com pastagem. O uso das técnicas multivariadas mostrou-se eficiente na distinção de ambientes sobre os sistemas de usos estudados.

Having in mind the importance of knowing the variability and spatial correlation of soil properties in Indian Dark Earth (IDE), we evaluated in this study the variability and the spatial correlation of aggregates and carbon in an Ultisol under coffee cultivation in southern Amazonas. It was established a 48 x 88 m sampling grid spaced 06 x 08 m, totalling 88 sampling points. Then soil samples were collected at: 0.0-0.05, 0.05-0.10, and 0.10-0.20 m layers. The spatial variability of the Mean Weighted Diameter (MWD) attributes, aggregates > 2 mm, < 2 mm, bulk density (BD) and organic carbon (OC) was analyzed by adjusting the simple semivariograms, while spatial correlations of the OC with aggregates and BD were analyzed by cross-semivariogram. We could conclude that there was spatial dependence in the variables, wherein the largest ones were observed at 0.0-0.05 m, except for Mean Weighted Diameter (MWD) and aggregates greater than 2.00 mm with larger range of values in depth from 0.05-0.10 and 0.10-0.20 m. The mean weight diameter and aggregate class attributes greater than 2.00 mm had negative spatial correlation with organic carbon at 0.0-0.05 m, while the smaller aggregates than 2.00 mm classes and bulk density correlated positively with organic carbon at 0.0-0.05 m and 0.10-0.20 m.

Indian Black Earths (IBEs) are distributed throughout the Amazon. They are characterized by their high chemical fertility and agricultural potential. IBEs have high organic carbon, favouring the improvement of soil structure. This work aimed to evaluate the aggregates and organic carbon (OC) spatial variability in different IBEs in southern Amazonas. We evaluated the organic carbon spatial variability, mean weight diameter (MWD), soil bulk density (Ïb) and aggregate classes under three uses of soil: pasture, cocoa, and coffee. We collected 528 soil samples in a point grid according to its use at two depths: 0.0-0.05 m and 0.10-0.20 m. Results were subjected to variance, descriptive, and geostatistical analyses. We concluded that the soil use influenced the IBEs physical attributes soil behavior, concentrating the higher values of CO, aggregates > 2.00 mm, and MWD at 0.0-0.05 m in relation to Ïb and aggregates < 2.00 mm where the higher values were the ones at 0.10-0.20 m. Aggregates< 2.00 mm (0.10-0.20 m) and OC (0.0-0.05 m) did not show spatial dependence, while the class of aggregates > 2.00 mm was the only attribute which represented to be a natural characteristic of the soil, with a strong spatial dependence, independently the land use and depth. There was no spatial relationship between the attributes studied and the geomorphic diversity.

Studies on the spatial behavior of soil attributes in the Amazon region are still very incipient. In this sense, the objective of this work was to evaluate the chemical attributes through multivariate techniques and geoestatistics in the area with agroforestry and sugarcane in Humaitá, AM, Brazil. The study was carried out in a farm in Humaitá city, Amazonas State. The studied area was divided into 70.00 m x 70.00 mmeshes with a regular spacing of 10 m, totaling 64 points and then, soil samples were collected at 0.0-0.2 m and 0.4-0.6 m depths. We performed chemical analyses of the attributes of soil. Then, it was applied descriptive statistics, multivariate and geostatistics. In conclusion, our findings suggest that for most of the chemical attributes was observed spatial dependence in both areas, with DSD varying from weak to moderate, with prevalence of the weak one. The multivariate analysis was efficient in the selection of chemical soil attributes that best represented the agroforestry environments and sugarcane. The results of this study will serve as a basis for further studies on these environments and other systems within the region; moreover serving as a basis for agricultural planning aiming a better environmental sustainability.